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commit0b73284c56upstream. Recently we notice that ext4 filesystem would occasionally fail to read metadata from disk and report error message, but the disk and block layer looks fine. After analyse, we lockon commit88dbcbb3a4("blkdev: avoid migration stalls for blkdev pages"). It provide a migration method for the bdev, we could move page that has buffers without extra users now, but it lock the buffers on the page, which breaks the fragile metadata read operation on ext4 filesystem, ext4_read_bh_lock() was copied from ll_rw_block(), it depends on the assumption of that locked buffer means it is under IO. So it just trylock the buffer and skip submit IO if it lock failed, after wait_on_buffer() we conclude IO error because the buffer is not uptodate. This issue could be easily reproduced by add some delay just after buffer_migrate_lock_buffers() in __buffer_migrate_folio() and do fsstress on ext4 filesystem. EXT4-fs error (device pmem1): __ext4_find_entry:1658: inode #73193: comm fsstress: reading directory lblock 0 EXT4-fs error (device pmem1): __ext4_find_entry:1658: inode #75334: comm fsstress: reading directory lblock 0 Fix it by removing the trylock logic in ext4_read_bh_lock(), just lock the buffer and submit IO if it's not uptodate, and also leave over readahead helper. Cc: stable@kernel.org Signed-off-by: Zhang Yi <yi.zhang@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20220831074629.3755110-1-yi.zhang@huawei.com Signed-off-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.